LM2907M-8/NOPB

LM2907M-8/NOPB 1 Features

Directly With Variable Reluctance MagneticPickups • Op Amp Has Floating Transistor Output •50-mA Sink or Source to Operate Relays,Solenoids, Meters, or LEDs • Frequency Doubling For Low Ripple • Tachometer Has Built-In Hysteresis With EitherDifferential Input or Ground Referenced Input±0.3% Linearity (Typical) • • Ground-Referenced Tachometer is Fully ProtectedFrom Damage Due to Swings Above VCC andBelow Ground • Output Swings to Ground For Zero FrequencyInput • Easy to Use; VOUT = fIN × VCC × R1 × C1 • Zener Regulator on Chip allows Accurate andStable Frequency to Voltage or CurrentConversion (LM2917)

LM2907M-8/NOPB 3 Description

The LM2907 and LM2917 devices are monolithicfrequency-to-voltage converters with a high gain opamp designed to operate a relay, lamp, or other loadwhen the inputfrequency reaches or exceeds aselected rate. The tachometer uses a charge pumplow-technique and offers frequency doubling forripple,full-input protection in two versions (8-pinLM2907 and LM2917), and its output swings toground for a zero frequency input.The op amp is fully compatible with the tachometerand has a floating transistor as its output. This featureallows either a ground or supply referred load of up to50 mA. The collector may be taken above VCC up to amaximum VCE of 28 V.The two basic configurations offered include an 8-pindevice with a ground-referenced tachometer inputand an internal connection between the tachometeroutput and the op amp noninverting input. Thisversion is well suited for single speed or frequencyswitching orfully buffered frequency-to-voltageconversion applications.Device Information(1)Minimum Component Tachometer Diagram

LM2907M-8/NOPB 2 Applications

• Over- and Under-Speed Sensing • Frequency-to-Voltage Conversion (Tachometer) • Speedometers • Breaker Point Dwell Meters • Hand-Held Tachometers • Speed Governors • Cruise Control • Automotive Door Lock Control • Clutch Control • Horn Control • Touch or Sound Switches

LM2907M-8/NOPB 5 Description (continued)

The more versatile configurations provide differential tachometer input and uncommitted op amp inputs. With thisversion the tachometer input may be floated and the op amp becomes suitable for active filter conditioning of thetachometer output.Both of these configurations are available with an active shunt regulator connected across the power leads. Theregulator clamps the supply such that stable frequency-to-voltage and frequency-to-current operations arepossible with any supply voltage and a suitable resistor.